Direction of seismic excitation

[mc_joah]

Hi,

According to EN 1998-1:2004 4.3.3.1 (11), the seismic excitation must be applied to all relevant directions.

For some structures there might be more than 2 relevant directions, and these directions may deviate from the directions of the global X- and Y-direction in the Robot model.

In my understanding of Robot, this should be possible when using the button "direction definition" in the "EN 1998 Parameters" dialog box.

I have tried this to a simple model, but it does not seem to work properly.

Have anyone tried something similar, with good results?

[Romanich]

Hi,

you must use Quadratic or Newmark combinations:

Also, you can read p.15.8 from Mr. Wilson book

[MARIOS75]

Keep in mind that unlike Newmark combination rule, SRSS rule is not direction dependant.

Rotating the building + newmark rule i guess will do the job.

[mark.martin.se]

Hi,....

....just to clarify,.... According to EC8 all the structure's members should "resist" 100% of the prescribed seismic forces in one direction plus 30%  of the prescribed forces in the perpendicular direction!

i.e.:

1Edx"+"0,3Edy

0,3Edx"+1Edy

when Z direction is disregarded.

So, what I need to check in the "Direction definition" is......

Am I wrong?

Regards

[tony.ridley]

You seem to have set it up correctly.